In the clinic, the combination of obesity and chronic obstructive pulmonary disease (COPD) has been increasing. However, whether high body mass index (BMI) affects the risk of exacerbations and pneumonias in individuals with COPD is presently unknown. Genetics can be used to assess the causal role of high BMI in exacerbations and pneumonias in individuals with COPD. We tested the hypothesis that high BMI is associated with an increased risk of exacerbations and pneumonias in individuals with COPD, both observationally and genetically.